The ecu is dead
Found some corrosion in the ecu connectors and hoped it was this, but no
Opened the ecu to find water damage:
Not much better after cleaning. These still work, so probably aren't the root cause
Corrosion on the connector
Even after cleaning with IPA it is still completely dead. The LWB has a unique ecu and there are none for sale anywhere, nor are there any standard FL1 4.2 A8 ecus available in the UK, although there are some for unpleasant prices in Europe. Luckily Marcel managed to find an FL1 A8 ecu in Poland so we're working on acquiring that. The next struggle of course will be working out how to code the immobiliser, which apparently needs the pin code from the old one
